It would be great if JQL could be improved to support wild card search in linkedIssues(issuekey, linktype) so you could search by project key. I.E. linkedissues("key-*").

Currently I just need a result set for all issues that have a linked issue of type "Duplicates". So perhaps just passing in the linktype with an empty value for issuekey would be an easier implementation. Or perhaps creating a new function that does this shouldn't be a difficult task.